50th anniversary of Apollo 11 – "We came in peace for all mankind"

In Europe, it was the middle of the night between Sunday, 20 July 1969 and Monday, 21 July, when, at 02:56 UTC, Neil Armstrong, commander of the Apollo 11 mission, stepped onto the surface of the Moon. Up to a billion people all around the world watched his exit from the Lunar Module, ‘Eagle’, on television. In the USA, it was television prime time on Sunday evening, 20 July. Twenty minutes later, astronaut Edwin ‘Buzz’ Aldrin also stepped onto the lunar surface. The image shows the first two people on the Moon – Aldrin, standing in front of Armstrong, and Armstrong, reflecting in Aldrin’s visor at the moment the photograph was taken.

On 16 July 1969 at 09:32 local time (13:32 UTC), the Saturn V rocket carrying the Apollo 11 mission lifted off from Launch Complex 39A at Kennedy Space Center on the east coast of Florida. Five engines (hence the name Saturn V) each produced a thrust of 7500 kilonewtons by burning 2500 kilograms of propellant per second. Only after 12 seconds did the rocket clear the launch tower. The first two stages and the first burn of the third stage brought the three Apollo 11 astronauts into Earth orbit. Subsequently, the third stage accelerated their spacecraft into a transfer orbit to the Moon, which it reached after three days.

When the three astronauts, Neil Armstrong (left), Michael Collins (centre) and Edwin ‘Buzz’ Aldrin – all born in 1930 – were selected for the Apollo 11 mission in January 1969, it was not yet clear that the mission planned for July of that year would land on the Moon. In the first half of the year, Apollo 9 was used to test the handling of the newly completed Lunar Module in Earth orbit. This was before Apollo 10 succeeded in a dress rehearsal in May – but not without a difficult situation after the descent of the lunar module to 15 kilometres above the lunar surface, when the Lunar Module unexpectedly rolled and turned over several times. After the safe return of Apollo 10, the way was clear for the first Moon landing in July 1969.

Michael Collins, the Command and Service Module pilot, designed the mission emblem for Apollo 11. It is the only mission emblem on which the names of the astronauts are not written at the edge, as was common practice on the Mercury and Gemini flights and the first three Apollo flights, as well as on subsequent missions. Collins wanted to show that the crew was flying to the Moon on behalf of all the 400,000 people who were involved in the construction of the launcher and the three spacecraft modules, the preparations and the planning. The bald eagle, the heraldic creature of the USA, holds an olive branch in its talons, which expresses the peaceful character of the mission. It has since been noticed that the Earth above the lunar horizon is illuminated by the Sun from the wrong direction during Apollo 11’s flight along the lunar equator. The hemisphere in shadow should be on the underside and not to the left.

Buzz Aldrin’s photograph of his footprint in the lunar dust is an icon of the 20th century. It was not taken to document the first footprints of the ‘Moon Boots’, but because Aldrin observed that the footprints had sharp edges and that the dust did not slip. Moon dust – referred to as regolith by geologists – does not consist of rounded granules, as is usually the case on Earth, but of microscopically small, jagged and easily interlocked particles that have strong cohesion. The unusual structure of the lunar dust results from micrometeorites that melt the regolith on impact, after which it solidifies again immediately.

When Neil Armstrong descended the ladder of the ‘Eagle’ Lunar Module, he unveiled a plaque on the landing leg to which the ladder was attached, with the inscription: “Here men from planet Earth first set foot on the Moon, July 1969, A. D. We came in peace for all mankind.” The engraved signatures are those of the three Apollo 11 astronauts (Neil A. Armstrong, Michael Collins, Edwin E. Aldrin) and the then President of the United States, Richard Nixon. The passage ‘in peace for all mankind’ was borrowed from a statement by the US Congress made on the foundation of NASA in 1958: “… it is the policy of the United States that activities in space should be devoted to peaceful purposes for the benefit of all mankind.”

20 July 1969. Charles Duke (left) has just given the order to land, the ‘go for landing’. Eleven minutes later, at 14:17 (Houston local time), the Lunar Module ‘Eagle’ with Neil Armstrong and Buzz Aldrin landed on the Moon. Duke’s reaction to the landing of Apollo 11 reported by Neil Armstrong (“The Eagle has landed.”) is frequently repeated: “Roger, Tranquillity. We copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot.” To the left of Duke are the astronauts Jim Lovell, commander of the Apollo 13 mission that flew in April 1970, and Fred Haise, Apollo 13 Lunar Module pilot.

The Apollo Program, aimed at landing humans on the Moon, was highly politically motivated. Only eight years before the first Moon landing, the USA had fallen behind the Soviet Union in the field of spaceflight. With the idea formulated by President John F. Kennedy in 1961, that the USA: “… should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth …” they not only wanted to overtake the USSR, but also demonstrate the superiority of the free, western world over the closed, dictatorial USSR. Enormous resources were made available and every effort was made. For NASA and its Apollo astronauts – who with one exception were pilots recruited from Air Force or Navy – planting the American flag next to the Lunar Module was far more than a symbolic act.

On 21 July 1969 (CET) the first two humans to walk on the Moon spent approximately two-and-a-half hours on the lunar surface. The landing site in the west of the Mare Tranquillitatis – a volcanic plain without many obstacles – was chosen for reasons of safety and lighting conditions. The Apollo 11 astronauts returned 22.5 kilograms of rock samples and lunar dust to Earth for the scientists. Their investigation was the prelude to extensive scientific work, lasting many years and rewarded with significant results, which culminated in a completely new understanding of the processes in the early Solar System during and after the formation of Earth-like bodies. In the foreground is Little West Crater. Neil Armstrong took some photographs here, about 60 metres from the Lunar Module, which were assembled into a mosaic. The crater should not be confused with the West Crater (550 metres further east), over the edge of which Neil Armstrong flew the Lunar Module under manual control to avoid landing in the field of boulders that surrounds the crater.

While Neil Armstrong and Buzz Aldrin were on the Moon, Michael Collins travelled around Earth’s natural satellite 18 times in an equatorial orbit. Every time he flew over the western Mare Tranquillitatis, he tried to observe the Eagle on the lunar surface from his orbit, which was at an altitude of approximately 100 kilometres, but he did not see it. Much later, the extremely high-resolution camera of the Lunar Reconnaissance Orbiter, which has been orbiting the Moon since 2009, succeeded in acquiring images of all six Apollo landing sites as well as the landing sites of the Soviet robotic Moon missions. To the right of the centre of the image is the descent stage of the Lunar Module, Neil Armstrong's footprints to the prominent Little West Crater, and south of the Lunar Module the seismometer experiment that was left behind.

The Apollo Program was an enormously fruitful project for planetary research. Robotic spacecraft from the Ranger, Lunar Orbiter and Surveyor series were sent to the Moon in preparation for safe landings, and transmitted thousands of images to Earth. What previously could only be observed with telescopes at a resolution no better than one or two kilometres could now be seen in images with a resolution more than 10 times higher in some cases. On the Moon, all six Apollo missions had extensive experimental packages with them, which left hardly anything to be desired by the geoscientists, astronomers and physicists involved. During the first Moon landing, a seismometer was installed that passively recorded vibrations of the lunar surface even after the mission – including the impact of the Lunar Module after its separation and descent to the surface.

The return of the Eagle to Columbia did not signify the end of the mission. Other mission-critical milestones were yet to come – docking with the Command and Service Module and igniting the engine to return to Earth from lunar orbit on the correct trajectory. After another three days, more critical tasks followed – re-entering Earth’s atmosphere at the correct angle to dissipate all the kinetic energy transferred to the system by the launcher and finally descending safely on parachutes to splash down in the ocean. The image shows the ‘Eagle’ in front of the lunar horizon with the dark outline of Mare Smythii and the ‘half Earth’ in the background.

On 24 July 1969 at 16:50 UTC – in the early hours of the morning local time – the Apollo 11 Command Module with the three astronauts on board splashed down in the western Pacific Ocean. Several helicopters had taken off from the aircraft carrier USS Hornet and navy divers immediately jumped from the helicopters into the ocean. They ‘boarded’ the capsule floating in the water, opened the hatch and helped the three somewhat exhausted but happy astronauts into inflatable boats. From there they were lifted into the helicopters and brought to the Hornet, which was 24 kilometres away. The mission lasted eight days.

President Richard Nixon travelled to the USS Hornet aircraft carrier before the return of the three Moon astronauts, in order to welcome the nation’s new heroes. However, the conversation had to take place through an intercom system, as Neil Armstrong, Michael Collins and Buzz Aldrin (from left to right) were quarantined for two weeks. Before the Apollo 11 mission, it was not clear whether the Moon, on whose surface scientists could not imagine live at all, might be home to microorganisms or viruses that could persist on Earth or even spread and cause great harm. For the astronauts, even more upsetting than the indirect contact with their president was the fact that it was not until 10 August 1969 that they were finally allowed to greet their families from the quarantine facility.

Credit:
NASA.

A look back at the Apollo 11 Moon landing mission.

The success of the mission meant that the USA had achieved the seemingly impossible – only eight years after John F Kennedy’s declaration, humans landed on the Moon and returned safely to Earth.

The three astronauts – Neil Armstrong, Edwin 'Buzz' Aldrin and Michael Collins – carried out the mission with the highest level of professionalism, making history in the process.

Focus: Crewed spaceflight, planetary research

The Saturn V rocket lifted off at an almost frighteningly slow speed at 09:32 local time (13:32 UTC) from Launch Complex 39A at the Kennedy Space Center, on the eastern coast of Florida. Every second, 13 tonnes of fuel were pumped into the five engines and burned; each of them produced 7500 kilonewtons of thrust. Twelve seconds later, the launcher cleared the launch tower. At 111 metres tall and weighing almost 3000 tonnes at launch, it was the most powerful rocket ever to have been built. Its lift-off was accompanied by a tremendous rumbling noise, the like of which had never been heard before from any human-made machine. Around one million people watched the launch from the local area. Atop the three-stage launcher was the Apollo 11 Command Module, Columbia, with the astronauts Neil Alden Armstrong, Edwin Eugene Aldrin and Michael Collins. They were scheduled to reach the Moon three days later. On the night of 20–21 July 1969, Neil Armstrong and Buzz Aldrin became the first human beings to set foot on the surface of the Moon. A thousand-year-old dream had come true!

Thousands of tonnes of fuel

The first stage burned for two-and-a-half minutes, carrying the launcher up to an altitude of 61 kilometres. From there, it sped towards space at a speed of 8000 kilometres per hour. Two thousand tonnes of fuel had now been burned, the stage separated and fell into the Atlantic Ocean, 560 kilometres west of the launch site. The second stage burned for another six minutes, before it too separated and fell into the sea, this time 4000 kilometres from Florida. The first burn of the third stage placed the Command Module, Service Module and Lunar Module in Earth orbit at an altitude of approximately 185 kilometres. There, the spacecraft orbited the planet for three hours at a speed of seven kilometres per second (25,000 kilometres per hour). Meanwhile, control of the spacecraft was transferred from Kennedy Space Center to Ground Control in Houston, Texas, for the remainder of the mission.

From Earth to the Moon in three days

At 16:22 UTC (17:22 CET), after one-and-a-half orbits of Earth, the spacecraft began its journey to the Moon. The Saturn IVB upper stage accelerated it to the required escape velocity of 11.2 kilometres per second. The most difficult manoeuvre on the journey to Earth’s satellite took place half an hour after injection into lunar transfer orbit. This was the separation of the Command and Service Module (CSM) from the third stage, followed by a 180-degree turn and the docking of the tip of the Command Module with the Lunar Module, so that it could be extracted from the third stage. After this, the now-connected components were again rotated by 180 degrees. Michael Collins, who was in charge of the manoeuvre, completed it without problems. The astronauts now had almost 400,000 kilometres left to travel.

The expended upper stage flew on its own trajectory past the Moon; it is still in orbit around the Sun. Telescopes on Earth have been able to use the reflection curves to detect the titanium oxide in the white paint and thus observe it on several occasions.

Time was short – NASA speeds up the pace and the risk

How was the Apollo 11 crew selected? Who decided which astronauts would be the first to fly to the Moon? And who determined who would be the first person to set foot on Earth's satellite? In one sense, the choice of Neil Armstrong, Buzz Aldrin and Michael Collins for the Apollo 11 mission was down to a lucky coincidence. Armstrong and Aldrin were the reserve crew for the Apollo 8 mission, which completed the very first journey to the Moon with a human crew at Christmas in 1968 and took the famous photograph of Earth appearing over the Moon's horizon – Earthrise.

The third substitute astronaut was originally Fred Haise, but Armstrong successfully petitioned Deke Slayton, the Assistant Director of Flight Crew Operations at NASA, for Michael Collins to take Haise's place. Collins had already proven his skills on Gemini 10. On 10 January 1969, Armstrong, Aldrin and Collins were presented to the public as the crew of Apollo 11. At this point, however, the Lunar Module had not even been tested, so it was by no means certain that Apollo 11 would land humans on the Moon.

But time was running out. NASA feared that the Soviet Union would soon be able to send the first cosmonauts to the Moon. The state of play was unclear following the surprise death of the Russian rocket engineer Sergei Korolev on 14 January 1966. In addition, there was President John F Kennedy's announcement on 25 May 1961, which committed the US to the goal of "… before this decade is out, landing a man on the Moon and returning him safely to the Earth." So, NASA was in a hurry – which increased the risk. The Apollo 6 and 7 missions, which took place in 1968, were unmanned test flights in Earth orbit. Apollo 8 in December 1968 marked the first time that the Saturn V rocket had been used, flying directly to the Moon with astronauts on board. In early 1969, NASA tested the completed Lunar Module in Earth orbit with Apollo 9. Apollo 10 in May 1969 was a dress rehearsal, with the Lunar Module descending to approximately 15 kilometres above the surface of the Moon. After all of this had gone smoothly, NASA was ready to attempt a landing with Apollo 11.

Armstrong, Aldrin, Collins – three exceptional people

Neil Armstrong was selected as the mission commander. He had also held this position on the Gemini mission in March 1966, when two spacecraft were docked together in space for the first time. That mission had almost ended in disaster, as the Gemini capsule began to tumble, but Armstrong brought the situation under control. He was seen as modest, almost introverted, but also extremely professional, exceptionally skilled, quick-thinking and a good team member. These were all qualities that NASA believed made him ideally suited to the command of Apollo 11. It was also clear that he, the commander and also a civilian, should be the first to set foot on the Moon. Edwin 'Buzz' Aldrin, the Lunar Module pilot, was known as more of a hothead – ambitious, an enthusiastic astronaut and no less capable than Armstrong. Other astronauts nicknamed him 'Dr Rendezvous'. While studying for a doctorate at the Massachusetts Institute of Technology in Boston, he wrote his thesis on the docking manoeuvre between two spacecraft, which had been carried out for the first time in the mid-1960s. Finally, Michael Collins, born in Rome, had performed a spacewalk as part of Gemini 10, and was considered to have a very even temperament. He also had an artistic streak – he designed the mission badge for Apollo 11, with an eagle landing on the Moon and holding an olive branch in its talons – a sign of peaceful intentions. All three were the same age – born in 1930 – and had gained experience as pilots in wartime and as former fighter jet test pilots in the US Air Force or Navy.

For three days, the Apollo mission flew without incident towards the Moon, whose gravitational field captured the capsule as planned. It was on a 'free-return trajectory'. This meant that after reaching the Moon, its gravity would allow the Command and Service Module to return to Earth, even in the event that its engine failed to fire. But everything went according to plan: At 17:21 CET on 19 July, the mission entered lunar orbit. Just 20 hours later, now on 20 July, Armstrong and Aldrin crawled from the 'Columbia' Command Module into the 'Eagle' Lunar Module and undocked from the Command and Service Module at 18:44. After further system tests and visual checks by Michael Collins – who watched the 'Eagle' rotating from the windows of the 'Columbia' – Neil Armstrong initiated the landing process with the words "The eagle has wings!"

Computer errors, boulders and manual control

The following quarter of an hour made space history. Armstrong and Aldrin – both standing and looking at the Moon out of the small triangular windows – soon realised, as they approached the surface while travelling from east to west, towards the volcanic plain of Mare Tranquillitatis, that they had passed the landmarks explored by for Apollo 10 several seconds too early. They were going to land several kilometres too far to the west. Five minutes after the engines had been ignited, while they were still 1800 metres above the Moon, the low-power yet robust on-board computer registered the famous 1201 and 1202 alarms, which did not strike Armstrong as particularly worrying. Mission control quickly issued a recommendation to ignore these alarms, which indicated the computer could no longer process the incoming data quickly enough.

Neil Armstrong took manual control of the Lunar Module. He saw a funnel-shaped crater with steep inner walls and metre-sized boulders around its edge at the intended landing site. Immediately, he realised that this place would be too dangerous for a landing and steered the Lunar Module over it. At the same time, he received the announcement via the Capsule Communicator (CapCom), astronaut Charles Duke, in Houston: "60 seconds!" The tank of the Lunar Module descent stage only had enough fuel for one more minute. Half a minute later: "30 seconds!" The mission was on the verge of being aborted. The Lunar Module was only three metres above the surface, and it was not certain that it would have been possible to abort without crashing onto the lunar surface. Neil Armstrong kept his cool and landed with enough fuel for only another 20 seconds. Buzz Aldrin called out “Contact light!” to Houston. Three seconds later the two astronauts shut down the engine, which had been whipping up dust.

The Eagle has landed, and Houston takes a deep breath

Twenty endless seconds later, the control centre was immensely relieved to receive Neil Armstrong's message: "Houston, Tranquillity Base here. The Eagle has landed." CapCom Duke replied, "Roger, Tranquillity. We copy you on the ground. You got a bunch of guys about to turn blue. We’re breathing again. Thanks a lot." It was Sunday, 20 July 1969 at 20:17 UTC (21:17 CET and mid-afternoon in the USA). Humans had landed on the Moon.

Shortly after midnight, German time – 21 July had already begun there, while the Moon landings took place in the evening of 20 July, US time, this being the best time for broadcasts – the astronauts in the Eagle began preparing the exit to the Moon. The hatch was opened at 03:38 CET. Neil Armstrong mounted the ladder at 03:51, climbed down it and, at 03:56:20 CET on 21 July 1969 stepped on the Moon and uttered the famous words, "That's one small step for man, one giant leap for mankind." Buzz Aldrin followed him 20 minutes later. For just over two hours, the first two men on the Moon explored the vast wasteland, collected 21.5 kilograms of moon rocks and samples of lunar dust, carried out the experiments that they had brought with them, and planted a United States flag. US President Richard Nixon congratulated them via a telephone connection from the White House in Washington D. C., transmitted via Houston.

Meanwhile, Michael Collins orbited the Moon 18 times, awaiting the return of his fellow astronauts. On 21 July at 18:54 CET, the upper part of the Lunar Module began its journey back to the Command and Service Module in lunar orbit. It docked with the CSM and then separated again after Armstrong and Aldrin had transferred to the Command Module. The Lunar Module crashed onto the Moon. Three days later, the astronauts splashed down safely in the Pacific Ocean and were picked up by helicopters from the aircraft carrier USS Hornet. As it was necessary to make sure that the astronauts had not brought any lunar microbes back to Earth, they had to undergo two weeks of quarantine.

The experiments and the descent stage of the Lunar Module remained on the Moon. A plaque on the landing leg beneath the exit ladder was unveiled by the two astronauts. It reads: “Here men from the planet Earth first set foot upon the Moon, July 1969, A. D. "We came in peace for all mankind."